At 70, Nancy Agronin has already suffered fractures from two falls - injuries that she attributes to having undergone intensive chemotherapy for breast cancer 17 years ago.

Her first fall came at age 65, seven years after her cancer diagnosis. Bone density screening at the time revealed that she had osteoporosis, which causes bones to become porous and fragile and puts her at a risk of fractures six times greater than average.

In February, she fell again, breaking a bone in her upper shoulder and tearing muscle by bracing herself. The San Carlos woman said her doctors did not discuss the effect of chemotherapy on her bones when she was treated for cancer. And although she admitted that wasn't at the top of her priorities at the time, she's certain her cancer treatment and her osteoporosis are linked.

"I really didn't realize the long-term effects of the chemotherapy," said Agronin, a retired registered nurse who is conscious about her health and exercises regularly.

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For many women treated for breast cancer, the risk of bone deterioration and future fragility comes almost as an afterthought. When faced with combatting a potentially deadly disease, jeopardizing future bone health is a concern, but not the biggest fear. In fact, it may not even be addressed before or during cancer treatment.

But with a growing population of patients expected to survive decades after cancer treatment, concerns about attending bone weakness are also increasing - especially with greater use of antihormonal therapies on top of chemotherapy, radiation and other treatments that contribute to bone density loss.

While more doctors are starting to address bone health, even during treatment, others can be so focused on the disease that they don't address the patient's overall health.

"For someone dealing with a devastating diagnosis and what can be a horrendous treatment process, it makes no sense at all to worry about those things in the moment," said Dr. Randall Stafford, director of the program on prevention outcomes and practices at the Stanford Prevention Research Center.

But Stafford said patients' bone and other health issues should be addressed more quickly. "For many breast cancer survivors, they really do get to the point where their breast cancer should recede as a prominent issue in their medical care, and yet sometimes it doesn't," he said. Bone health is an issue primarily in breast cancer patients because the majority of women have tumors that feed off the female hormone estrogen.

Estrogen at risk

Women's estrogen - and by definition their bones - may be assaulted on multiple fronts. They may undergo treatments that force them into menopause, accompanied or followed by antiestrogen therapies. These drugs can also have a deleterious effect on bones.

Studies have shown an increase in fracture risk among postmenopausal women because of low bone density and accelerated bone loss after chemotherapy.

Likewise, the male hormone testosterone also supports bone health. So men taking hormone-blocking drugs - known as androgen-deprivation therapy - for prostate cancer also face the risk of osteoporosis. Men typically get osteoporosis at a much later age than women, but these hormonal therapies fast-forward that chance.

"We're very attentive of the side-effect issues, especially now that men are living longer and longer on treatment," said Dr. Matthew Cooperberg, assistant professor of urology at UCSF and a urologic cancer expert at the UCSF Helen Diller Family Comprehensive Cancer Center.

For women undergoing breast cancer treatment, a key factor in deciding which treatments to use and how to protect their bones depends on whether they have gone through menopause, be it naturally or through treatment.

Drug treatments

Premenopausal women are generally placed on tamoxifen, which is in a class called selective estrogen-receptor modulators. The drug selectively targets the estrogen hormone that fuels the cancer. The treatment seems to have an inconsequential effect on bone health, although that's up for debate.

Women who have already gone through menopause are often placed on a newer class of drugs called aromatase inhibitors, such as Arimidex, which are effective against the cancer but can increase their risk of developing osteoporosis and arthritis.

"Aromatase inhibitors are antiestrogenic, and they cause bone loss. We do not use aromatase inhibitors on premenopausal women," said Dr. Risa Kagan, an East Bay gynecologist and certified menopause specialist who treats breast cancer patients and serves on the medical and scientific advisory board of American Bone Health. "The effect of tamoxifen in a premenopausal woman ... can make some women lose a little bone, but it's not that significant."

Some health experts are not so sure. They point to studies that have shown that while selective estrogen-receptor modulators, like tamoxifen, are designed to protect the bones, women who have gone through treatment still have a greater risk of fractures than those who have not.

"The purpose of the (selective estrogen-receptor modulator) is to protect the bone while you're blocking the breast from being stimulated from estrogen," said Marcia Stefanick, professor of medicine at the Stanford Prevention Research Center. "They don't do a good enough job in protecting the bone, and the aromatase inhibitors are even worse."

A patient's plight

For patients, the choices can be frustrating.

Niki Calastas of Redwood Shores was diagnosed with breast cancer 2 1/2 years ago at age 31 and underwent chemotherapy, radiation and a double mastectomy.

Calastas, whose treatment did not bring on early menopause, is in the middle of a five-year course of tamoxifen to prevent a recurrence of cancer. She has discussed removing her ovaries as a further precaution, but that would put her into immediate menopause. She has resisted that option so far.

With a family history of osteoporosis, Calastas makes sure to undergo regular bone scans. The tests have been normal, but she's aware of the risks. "I do not want to have osteoporosis, but you have to pick and choose your battles," she said.

Steps can be taken to mitigate the risk of bone loss. Medications plus supplements such as vitamin D and calcium may be used for men and women undergoing hormonal therapies to combat the risk of bone loss, both during and after treatment.

Stanford's Stafford said patients need to take charge of their long-term health. "If a woman was diagnosed with breast cancer 10 years ago and hasn't had any signs of recurrence, the most likely way she's going to die is going to be heart disease," he said. "It's not going to be a recurrence of her breast cancer."

Agronin has taken this message to heart by taking vitamin D and calcium supplements, going to the gym regularly and teaching a "Sit and Be Fit" class at her local adult community center three mornings a week. She also serves on the San Mateo County Fall Prevention Task Force.

She's aware that there's only so much she can do. Still, she said, "it's better to have your feet on the ground than in the ground."

About osteoporosis

What is osteoporosis? A disease in which the bones become weak and are more likely to break.

What are the risk factors? Age, premature menopause or other change in sex hormones, family history, low body weight, cigarette smoking or excessive alcohol use, chemotherapy and other specific medications, prolonged inactivity.

What are the symptoms? Osteoporosis is called the "silent disease" because bone is lost with no signs. Many people learn they have the disease after a fracture.

How can it be treated? There is no true cure for osteoporosis. But it can be prevented or helped with certain medications, exercise, proper nutrition, calcium and vitamin D supplements.